Breast cancer and prostate cancer are overwhelmingly the most common hormone dependent malignancies of men and women. Substantial progress has been made in research leading to identification of specific genetic elements whose mutation, deletion, amplification or rearrangement contribute to the pathogenesis of the diseases. This includes both new data on expression of dominantly acting oncogenes such as erbBl, erbB2, and erbB3, and the loss of repressive genetic elements such as NM23, P53, and Rb. The mechanisms by which these genetic elements interact with proliferative controls to induce abnormal growth and malignant behavior is also rapidly advancing. This meeting will be aimed at developing consensus on the mechanisms of involvement of these genetic elements in breast and prostate disease and the impact of this information on approaches to diagnosis, prognosis, and therapy. A central, novel feature of this meeting will be to assemble scientists interested in both breast and prostate cancer to facilitate cross-fertilization of ideas. Both breast and prostate cancer depend upon steroid hormones for onset and progression. Progression of both cancer types also depends on interaction of growth factors and progressive genetic changes in oncogenes and anti-oncogenes. This conference provides a unique opportunity to invite the leaders in cellular and molecular studies of each field to compare data, modify their working hypotheses of regulation of malignancies, and discuss new therapeutic approaches. These two diseases together afflict approximately 10% of both men and women and have remarkable similarities in the biology of their onset and in therapeutic strategies.